The invention relates generally to multilateral well operations. More particularly, the invention relates to a method and apparatus for accessing a branch of a multilateral well.
A multilateral well, also known as a multi-branch well, is a well having one or more lateral boreholes branching off a single primary wellbore. The primary wellbore may be vertical, horizontal, or deviated. The lateral boreholes may branch off the primary wellbore in any number of directions to allow production from several target reservoirs or formations through the primary wellbore. Multilateral wells are advantageous in comparison to single wells in that their lateral boreholes can be brought into close contact with several target reservoirs, thereby allowing production from the reservoirs to be maximized.
Tubulars are often installed in lateral boreholes. For example, in unconsolidated or weakly consolidated formations, liners are often installed in lateral boreholes to prevent the boreholes from collapsing. After such installation, it is often desirable to re-enter the tubular in order to perform one or more operations in the lateral borehole. Such re-entry operations generally include inserting a downhole tool into the tubular. In some cases, there may be eccentricity between the tubular and the lateral borehole, for example, due to formation washout. In this case, there is the likelihood that a downhole tool inserted into the lateral borehole would be misaligned with the tubular and may not be able to enter the tubular or may even become stuck in between the tubular and the lateral borehole.
From the foregoing, a method of assuring entry of a downhole tool into a tubular in a lateral borehole would be useful.